The surgical treatment of glaucoma remains a challenging subject. Patients with progressive visual field and optic nerve damage, despite maximal tolerated medical therapy and laser treatment, have traditionally been offered surgical approaches to the regulation of their intraocular pressure only as a last resort. For the most part, this was because of the high complication and failure rates of surgical approaches and the consequent increased risk-to-benefit ratio associated with surgery. Recently, the advent of antimetabolite agents has increased the effectiveness of primary surgical approaches, but has introduced a new set of potential complications and attendant risks.
Current implants used for the regulation of intraocular pressure are associated with a number of problems. They are generally difficult to implant, requiring a long learning curve for a typical surgeon to become comfortable with their use. Current designs are also cumbersome, often requiring several different procedures or surgeries in order to insure proper functioning of the implant. Frequent medical complications are experienced with all current designs of ocular implants for the regulation of intraocular pressure. Currently available implants are also poorly, if at all, adjustable in the amount of filtration which may be achieved through their use.
For these and many other reasons, many ophthalmologists remain disillusioned about the prospect of regulating intraocular pressure through the use of a surgical implant.
Examples of prior ocular implants useful for reducing intraocular pressure include those disclosed in U.S. Pat. Nos. 4,402,681, 5,178,604, 5,041,081, 5,171,213, 4,634,418, 4,886,488, 5,041,081.